We assessed delayed dermal hypersensitivity to varicella-zoster virus by a varicella skin test in 12 patients (nine women and three men ranging in age from 27 to 85 years) with ophthalmic herpes zoster during the acute stage and in a group of 27 healthy controls (15 women and 12 men ranging in age from 18 to 58 years). Of the 27 healthy individuals, 25 had positive skin test reactions whereas only one of the 12 patients with ophthalmic herpes zoster had a positive skin test reaction within two weeks after the onset of the eruption, suggesting that cellular immunity to varicella-zoster virus antigens is impaired in the development of ophthalmic herpes zoster. Our study also showed that the varicella skin test is a convenient way to diagnose ophthalmic herpes zoster during the acute stage of the disease.